1. Field of the Invention
The present invention relates to a solenoid switch, and more particularly, to a latch type solenoid switch plated with anti-corrosion material and a method of plating the solenoid switch.
2. Description of the Related Art
A solenoid switch operates by magnetic forces applied by a permanent magnet and an electromagnet. FIG. 1 illustrates the structure of a general latch type solenoid switch.
Referring to FIG. 1, the solenoid switch includes a coil unit 10, a frame 20, a permanent magnet 30 and a moving part 40. The coil unit 10 includes a coil 12 wound around a cylindrical bobbin 11, and when current is supplied to the coil unit 10, a magnetic field is generated in a direction opposite to a magnetic field of the permanent magnet 30. A section of the moving part 40 is inserted into the bobbin 11, and is elastically biased away from the permanent magnet 30 by a spring 50.
In the above structure, when current is not supplied to the coil unit 10, the moving part 40 adheres to the frame 20 due to force acting thereon in the magnetic field of the permanent magnet 30. When current is supplied to the coil unit 10, a magnetic field opposite to that of the permanent magnet 30 is generated in the coil unit 10, and the moving part 40 is detached from the frame 20 by the restoration force of the spring 50. In this way, depending on the current supply to the coil unit 10, the moving part 40 moves in the directions indicated by the arrow in FIG. 1.
In general, the frame 20 and the moving part 40 are made of steel and are plated to prevent corrosion. The layer of plating has a thickness of about 3 μm, which is very thin. If the layer of plating is too thin, chemical resistance to salt in sweat from people's hands may be too weak. In order to increase resistance against corrosion, a sufficiently thick layer of plating is necessary, but if the layer is too thick, there is a possibility of reducing the adhesion force between the moving part 40 and the frame 20 by shielding the moving part 40 from the magnetic field of the permanent magnet 30.